The present invention relates to the patient rehabilitation art. The invention finds particular application in the rehabilitation and physical therapy for injured limbs and joints and will be described with particular reference thereto. It is to be appreciated that the invention may find broader applications in other areas of patient rehabilitation, such as recovery from orthopedic surgery, circulatory stimulation, muscle rehabilitation, and the like.
In the past, postoperative and post trauma treatment of patients' joints commonly included immobilization. The affected joints were fixed by casts or traction for an extended duration. During the immobilization, various medical problems commonly arose associated with the immobilized joint and body portions. In particular, capsular, ligamentous, and articular adhesions, thromboembolism, venous stasis, post-traumatic osteopenia, peripheral edema muscle atrophy, and the like were commonly attributed to the immobilization.
These immobilization related medical problems could be reduced or eliminated by early mobilization of the affected joint. It has been found to be advantageous to initiate joint mobilization immediately following orthopedic surgery, in many instances in the operating and recovery rooms while the patient is still under anethesia. Specifically, continuous passive motion of the affected joints have been found to be effective in reducing or eliminating the above-referenced medical problems, promoting faster healing, reducing the amount of pain and the associated requirement for pain medications, improving the range of movement of the affected joint after recovery, and the like.
An early passive motion apparatus for knee surgery included a bicycle pedal arrangement. The pedals were driven by an appropriate drive means to flex the patient's knee.
Subsequently, more sophisticated apparatus were developed that could be used while the patient was still in bed. A super structure was fastened over the bed supporting a series of pulleys, a motor, and an adjustable lever arm driven by the motor. A rope extended from the lever arm around the pulleys and supported a sling positioned around the knee of the patient. As the motor drove the lever arm, the rope and sling arrangement lifted and lowered the knee. Among the drawbacks of this system was the relatively long set-up time required and the cumbersome nature of the apparatus.
Subsequently, simpler bed and floor supported apparatus were developed. In one, a motor driven worm gear drove a foot pedal toward and away from the patient. When the patient's foot was positioned adjacent the pedal, the pedal pushed and pulled on the patient's foot so as to raise and lower the patient's knee. One of the problems associated with the driven foot pedal apparatus was that the knee joint was subjected to undesirable compressive forces.
To alleviate compression of the knee, other apparatus were developed in which the worm gear drove an articulated leg supporting structure. A thigh supporting portion was connected to a calf supporting portion by a simple pivot. A follower on the worm gear selectively caused the thigh and calf portions to be pivoted upward and extended outward flexing the patient's knee therewith. One of the problems with the simply pivoted leg supporting structure was that the pivotable movement did not match the movement of the human knee. This mismatch in the movement of the knee and the leg supporting structure caused portions of the leg to slide or move longitudinally relative thereto. Moreover, the worm gear driven continuous passive motion exercise structures were relatively bulky and required relatively large storage areas between exercise sessions. The bulky size was particularly disadvantageous in relatively confined hospital rooms in which storage space was precious.
The present invention provides a new and improved continuous passive motion exercise apparatus which overcomes the above-referenced problems and others.